Chrysippus’ chief astronomical contribution was his cosmology, which served as the dominant paradigm until the time of astronomer Ptolemy (circa 150).

Chrysippus was born under the rule of Ptolemy II (the Greek king of Egypt); but his family was Kilikian (a Semitic people), and he learned Greek before he moved (at about 20) to Athens. There he studied philosophy under the Stoic scholarch Kleanthes (the name “Chrys-ippos,” meaning “gold-steed,” may translate his native name). From 232 BCE until his death, Chrysippus was scholarch of the Stoa, one of the four major schools of philosophy in Athens.

Chrysippus wrote extensively on Stoic philosophy – 90 % of all Stoic writings in the third century BCE were by him – covering astronomical topics in such works as On the Kosmos, On Motion, On Nature, and On the Void through which he standardized Stoic doctrines. (His writings are now preserved solely in extracts.)